Thermal decomposition mechanism of ammonium sulfate catalyzed by ferric oxide

It was demonstrated that iron molybdate catalysts for methanol oxidation can be prepared using Fe(II) as a precursor instead of Fe(III). This would allow for reduction of acidity of preparation solutions as well as elimination of Fe(III) oxide impurities which are detrimental for the process selectivity. The system containing Fe(II) and Mo(VI) species in aqueous solution was investigated using UV-Vis spectroscopy. It was demonstrated that three types of chemical reactions occur in the Fe(II)-Mo(VI) system: (i) formation of complexes between Fe(II) and molybdate(VI) ions, (ii) inner sphere oxidation of coordinated Fe(II) by Mo(VI) and (iii) decomposition of the Fe-Mo complexes to form scarcely soluble Fe(III) molybdate, Mo(VI) hydrous trioxide and molybdenum blue. Solid molybdoferrate(II) prepared by interaction of Fe(II) and Mo(VI) in solution was characterized by EDXA, TGA, DTA and XRD and a scheme of its thermal evolution proposed. The iron molybdate catalyst prepared from Fe(II) precursor was tested in methanol-toformaldehyde oxidation in a continuous flow fixed-bed reactor to show similar activity and selectivity to the conventional catalyst prepared with the use of Fe(III).

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“…The exothermic peak at 400-440°C may be explained by the decomposition of ammonium pyrosulfate (Eq. (6)) [23,24].…”

Section: Synthesis Of Ammonium Molybdoferrate(ii)mentioning

confidence: 99%

Preparation of iron molybdate catalysts for methanol to formaldehyde oxidation based on ammonium molybdoferrate(II) precursor

Николенко

Kozhevnikov

Kostyniuk

et al. 2018

Journal of Saudi Chemical Society

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“…It is a well water-soluble, inorganic salt (facilitating cleaning) hardly soluble in edible oils and fats. It is made from various sources and exists in various grades (Song et al, 2013). Some is produced by reacting ammonia with sulfuric acid or by addition of ammonium carbonate solution to gypsum (calcium carbonate being precipitated and leaving ammonium sulphate in solution).…”

Section: Chemical Properties and Usementioning

confidence: 99%

“…Ammonium sulphate decomposes at temperatures above about 230°C, first to ammonium bisulphate, then to ammonium pyrosulphate and finally to gases including ammonia and sulfur dioxide (Song et al, 2013). In an environment of reactive components, reactions may occur at lower temperatures.…”

Section: Reactivity and Reaction Productsmentioning

confidence: 99%

Scientific opinion on the evaluation of substances as acceptable previous cargoes for edible fats and oils

Knutsen¹,

Alexander²,

Barregård³

et al. 2017

EFS2

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Shipping of edible fats and oils into Europe is permitted in bulk tanks, provided that the previous cargo is included in a positive list. The European Commission requested EFSA to evaluate the acceptability as previous cargoes for fats and oils the substances calcium lignosulphonate, methyl acetate, ethyl tertbutyl ether (ETBE) and ammonium sulphate. The evaluation was based on the same criteria as those used for the evaluation of the substances currently on the list in the Annex to Commission Directive 96/ 3/EC as acceptable previous cargoes for edible fats and oils. Methyl acetate and ETBE meet the criteria for acceptability as previous cargoes. Due to uncertainties, mainly with regard to the composition and toxicity of the low molecular mass fraction, and the fact that the toxicological database is limited to the 40-65 grade and does not cover all grades of calcium lignosulphonate shipped as previous cargoes, the EFSA Panel on Contaminants in the Food Chain (CONTAM Panel) concluded that calcium lignosulphonate does not meet the criteria for acceptability as a previous cargo. Only food-grade ammonium sulphate meets the criteria for acceptability as a previous cargo due to uncertainties about impurities in other (non-food) grades.

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“…However, large amounts of (NH 4 ) 2 SO 4 are produced in the typical caprolactam process, and 1 ton of caprolactam product will release 1.5–2.0 tons of ammonium sulfate as an undesirable byproduct . Additionally, the production and demand of caprolactam is increasing rapidly every year, resulting in the overproduction of ammonium sulfate . Therefore, several new caprolactam technologies with less or non-(NH 4 ) 2 SO 4 byproduct have been investigated and brought forward, such as vapor-phase Beckmann rearrangement over solid catalysts − and the liquid-phase Beckmann rearrangement over solid − or organic catalysts. − Unfortunately, very few industrial applications have been reported about these technologies, due to the practical problems including serious catalyst deactivation, poor catalytic efficiency, low selectivity, etc.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic Modeling of CaSO₄–(NH₄)₂SO₄–NH₃–H₂O Quaternary System with Asymmetric E-NRTL Model

Pan

Liu

Qin

et al. 2019

Ind. Eng. Chem. Res.

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Ammonium sulfate [(NH 4 ) 2 SO 4 ], an undesired byproduct in the caprolactam process, can be converted into recyclable NH 3 by the substitution reaction with lime milk to reduce the ammonia consumption and produce high-quality gypsum. However, the thermodynamic mechanism of this process has not been clarified, which results in the unpredictable crystal phase of calcium sulfate products. In this work, a thermodynamic model for the CaSO 4 −(NH 4 ) 2 SO 4 −NH 3 −H 2 O quaternary system with the asymmetric E-NRTL activity coefficient model was developed to understand the thermodynamic behavior. The modeling works involved the data fitting of binary solubility, osmotic coefficient, enthalpy of solution, and heat capacity data as well as ternary solubility data. It was shown that the model could predict the solubility of ammonia and calcium sulfate in aqueous ammonium sulfate solution with temperature ranging from 0 to 160 °C and pressure up to 1.0 MPa. Furthermore, the constructed model for the quaternary system was proved to be reliable for predicting the phase transition behavior of solid CaSO 4 in the electrolyte mixtures of (NH 4 ) 2 SO 4 −NH 3 −H 2 O solution. For the regeneration process of NH 3 from ammonium sulfate, this work will offer a reliable model for the reactors design and process optimization.

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Thermal decomposition mechanism of ammonium sulfate catalyzed by ferric oxide

Cited by 16 publications

References 9 publications

Preparation of iron molybdate catalysts for methanol to formaldehyde oxidation based on ammonium molybdoferrate(II) precursor

Preparation of iron molybdate catalysts for methanol to formaldehyde oxidation based on ammonium molybdoferrate(II) precursor

Scientific opinion on the evaluation of substances as acceptable previous cargoes for edible fats and oils

Thermodynamic Modeling of CaSO₄–(NH₄)₂SO₄–NH₃–H₂O Quaternary System with Asymmetric E-NRTL Model

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Thermal decomposition mechanism of ammonium sulfate catalyzed by ferric oxide

Cited by 16 publications

References 9 publications

Preparation of iron molybdate catalysts for methanol to formaldehyde oxidation based on ammonium molybdoferrate(II) precursor

Preparation of iron molybdate catalysts for methanol to formaldehyde oxidation based on ammonium molybdoferrate(II) precursor

Scientific opinion on the evaluation of substances as acceptable previous cargoes for edible fats and oils

Thermodynamic Modeling of CaSO4–(NH4)2SO4–NH3–H2O Quaternary System with Asymmetric E-NRTL Model

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Product

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About

Thermodynamic Modeling of CaSO₄–(NH₄)₂SO₄–NH₃–H₂O Quaternary System with Asymmetric E-NRTL Model